package day2;

import java.util.Scanner;

public class Day02_02 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] cost = new int[n];
        cost[0] = in.nextInt();

        int[] dp = new int[n+1];

        for(int i = 2; i <= n; i++) {
            cost[i-1] = in.nextInt();
            dp[i] = Math.min(dp[i-1] + cost[i-1], dp[i-2] + cost[i-2]);
        }
        System.out.println(dp[n]);
    }
}
//https://www.nowcoder.com/practice/9b969a3ec20149e3b870b256ad40844e?tpId=230&tqId=39751&ru=/exam/oj